Merge changes from topic "oct16b"

* changes:
  Recommend efficient String operations.
  Simple alternative to String.format().

3 files changed, 308 insertions, 0 deletions

diff --git a/errorprone/java/com/google/errorprone/bugpatterns/android/EfficientStringsChecker.java b/errorprone/java/com/google/errorprone/bugpatterns/android/EfficientStringsChecker.java
new file mode 100644
index 000000000000..3fbd51deec65
--- /dev/null
+++ b/errorprone/java/com/google/errorprone/bugpatterns/android/EfficientStringsChecker.java
@@ -0,0 +1,146 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.errorprone.bugpatterns.android;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.matchers.Matchers.allOf;
+import static com.google.errorprone.matchers.Matchers.contains;
+import static com.google.errorprone.matchers.Matchers.kindIs;
+import static com.google.errorprone.matchers.Matchers.methodInvocation;
+import static com.google.errorprone.matchers.Matchers.not;
+import static com.google.errorprone.matchers.Matchers.staticMethod;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.predicates.TypePredicate;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.LiteralTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.Tree.Kind;
+import com.sun.tools.javac.code.Symbol.VarSymbol;
+import com.sun.tools.javac.code.Type;
+
+import java.util.List;
+
+/**
+ * Android offers several efficient alternatives to some upstream {@link String}
+ * operations.
+ */
+@AutoService(BugChecker.class)
+@BugPattern(
+    name = "AndroidFrameworkEfficientStrings",
+    summary = "Verifies efficient Strings best-practices",
+    severity = WARNING)
+public final class EfficientStringsChecker extends BugChecker
+        implements MethodInvocationTreeMatcher {
+
+    private static final Matcher<ExpressionTree> FORMAT_CALL = methodInvocation(
+            staticMethod().onClass("java.lang.String").named("format"));
+    private static final Matcher<ExpressionTree> PRECONDITIONS_CALL = methodInvocation(
+            staticMethod().onClass(withSimpleName("Preconditions")).withAnyName());
+    private static final Matcher<ExpressionTree> OBJECTS_CALL = methodInvocation(
+            staticMethod().onClass("java.util.Objects").named("requireNonNull"));
+
+    /**
+     * Match an expression which combines both string literals any other dynamic
+     * values, since these allocate a transparent StringBuilder.
+     * <p>
+     * This won't match a single isolated string literal, or a chain consisting
+     * of only string literals, since those don't require dynamic construction.
+     */
+    private static final Matcher<ExpressionTree> CONTAINS_DYNAMIC_STRING = allOf(
+            contains(ExpressionTree.class, kindIs(Kind.STRING_LITERAL)),
+            contains(ExpressionTree.class, not(kindIs(Kind.STRING_LITERAL))));
+
+    @Override
+    public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+        if (FORMAT_CALL.matches(tree, state)) {
+            // Skip over possible locale to find format string
+            final List<? extends ExpressionTree> args = tree.getArguments();
+            final ExpressionTree formatArg;
+            final List<VarSymbol> vars = ASTHelpers.getSymbol(tree).params();
+            if (vars.get(0).type.toString().equals("java.util.Locale")) {
+                formatArg = args.get(1);
+            } else {
+                formatArg = args.get(0);
+            }
+
+            // Determine if format string is "simple" enough to replace
+            if (formatArg.getKind() == Kind.STRING_LITERAL) {
+                final String format = String.valueOf(((LiteralTree) formatArg).getValue());
+                if (isSimple(format)) {
+                    return buildDescription(formatArg)
+                            .setMessage("Simple format strings can be replaced with "
+                                    + "TextUtils.formatSimple() for a 6x performance improvement")
+                            .build();
+                }
+            }
+        } else if (PRECONDITIONS_CALL.matches(tree, state)
+                || OBJECTS_CALL.matches(tree, state)) {
+            final List<? extends ExpressionTree> args = tree.getArguments();
+            for (int i = 1 ; i < args.size(); i++) {
+                final ExpressionTree arg = args.get(i);
+                if (CONTAINS_DYNAMIC_STRING.matches(arg, state)) {
+                    return buildDescription(arg)
+                            .setMessage("Building dynamic messages is discouraged, since they "
+                                    + "always allocate a transparent StringBuilder, even in "
+                                    + "the successful case")
+                            .build();
+                }
+            }
+        }
+        return Description.NO_MATCH;
+    }
+
+    static boolean isSimple(String format) {
+        for (int i = 0; i < format.length(); i++) {
+            char c = format.charAt(i);
+            if (c == '%') {
+                i++;
+                c = format.charAt(i);
+                switch (c) {
+                    case 'b':
+                    case 'c':
+                    case 'd':
+                    case 'f':
+                    case 's':
+                    case 'x':
+                    case '%':
+                        break;
+                    default:
+                        return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    static TypePredicate withSimpleName(final String filter) {
+        return new TypePredicate() {
+            @Override
+            public boolean apply(Type type, VisitorState state) {
+                return type.tsym.getSimpleName().toString().equals(filter);
+            }
+        };
+    }
+}
diff --git a/errorprone/tests/java/com/google/errorprone/bugpatterns/android/EfficientStringsCheckerTest.java b/errorprone/tests/java/com/google/errorprone/bugpatterns/android/EfficientStringsCheckerTest.java
new file mode 100644
index 000000000000..a755564d52dd
--- /dev/null
+++ b/errorprone/tests/java/com/google/errorprone/bugpatterns/android/EfficientStringsCheckerTest.java
@@ -0,0 +1,119 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.errorprone.bugpatterns.android;
+
+import static junit.framework.Assert.assertFalse;
+import static junit.framework.Assert.assertTrue;
+
+import com.google.errorprone.CompilationTestHelper;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class EfficientStringsCheckerTest {
+    private CompilationTestHelper compilationHelper;
+
+    @Before
+    public void setUp() {
+        compilationHelper = CompilationTestHelper.newInstance(
+                EfficientStringsChecker.class, getClass());
+    }
+
+    @Test
+    public void testSimple() {
+        assertTrue(EfficientStringsChecker.isSimple(""));
+        assertTrue(EfficientStringsChecker.isSimple("%s"));
+        assertTrue(EfficientStringsChecker.isSimple("String %s%s and %%%% number %d%d together"));
+
+        assertFalse(EfficientStringsChecker.isSimple("%04d"));
+        assertFalse(EfficientStringsChecker.isSimple("%02x:%02x:%02x"));
+    }
+
+    @Test
+    public void testFormat() {
+        compilationHelper
+                .addSourceLines("Example.java",
+                        "import java.util.Locale;",
+                        "public class Example {",
+                        "  public void example(String str) {",
+                        "    String.format(str, str);",
+                        "    // BUG: Diagnostic contains:",
+                        "    String.format(\"foo %s bar\", str);",
+                        "    // BUG: Diagnostic contains:",
+                        "    String.format(\"foo %d bar\", 42);",
+                        "    String.format(\"foo %04d bar\", 42);",
+                        "  }",
+                        "  public void exampleLocale(String str) {",
+                        "    String.format(Locale.US, str, str);",
+                        "    // BUG: Diagnostic contains:",
+                        "    String.format(Locale.US, \"foo %s bar\", str);",
+                        "    // BUG: Diagnostic contains:",
+                        "    String.format(Locale.US, \"foo %d bar\", 42);",
+                        "    String.format(Locale.US, \"foo %04d bar\", 42);",
+                        "  }",
+                        "}")
+                .doTest();
+    }
+
+    @Test
+    public void testPreconditions() {
+        compilationHelper
+                .addSourceFile("/android/util/Preconditions.java")
+                .addSourceLines("Example.java",
+                        "import android.util.Preconditions;",
+                        "import java.util.Objects;",
+                        "public class Example {",
+                        "  String str;",
+                        "  public void checkState(boolean val) {",
+                        "    Preconditions.checkState(val);",
+                        "    Preconditions.checkState(val, str);",
+                        "    Preconditions.checkState(val, \"foo\");",
+                        "    Preconditions.checkState(val, \"foo\" + \"bar\");",
+                        "    // BUG: Diagnostic contains:",
+                        "    Preconditions.checkState(val, \"foo \" + val);",
+                        "  }",
+                        "  public void checkArgument(boolean val) {",
+                        "    Preconditions.checkArgument(val);",
+                        "    Preconditions.checkArgument(val, str);",
+                        "    Preconditions.checkArgument(val, \"foo\");",
+                        "    Preconditions.checkArgument(val, \"foo\" + \"bar\");",
+                        "    // BUG: Diagnostic contains:",
+                        "    Preconditions.checkArgument(val, \"foo \" + val);",
+                        "  }",
+                        "  public void checkNotNull(Object val) {",
+                        "    Preconditions.checkNotNull(val);",
+                        "    Preconditions.checkNotNull(val, str);",
+                        "    Preconditions.checkNotNull(val, \"foo\");",
+                        "    Preconditions.checkNotNull(val, \"foo\" + \"bar\");",
+                        "    // BUG: Diagnostic contains:",
+                        "    Preconditions.checkNotNull(val, \"foo \" + val);",
+                        "  }",
+                        "  public void requireNonNull(Object val) {",
+                        "    Objects.requireNonNull(val);",
+                        "    Objects.requireNonNull(val, str);",
+                        "    Objects.requireNonNull(val, \"foo\");",
+                        "    Objects.requireNonNull(val, \"foo\" + \"bar\");",
+                        "    // BUG: Diagnostic contains:",
+                        "    Objects.requireNonNull(val, \"foo \" + val);",
+                        "  }",
+                        "}")
+                .doTest();
+    }
+}
diff --git a/errorprone/tests/res/android/util/Preconditions.java b/errorprone/tests/res/android/util/Preconditions.java
new file mode 100644
index 000000000000..558cdaf483a4
--- /dev/null
+++ b/errorprone/tests/res/android/util/Preconditions.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.util;
+
+public class Preconditions {
+    public static void checkArgument(boolean expression) {
+        throw new UnsupportedOperationException();
+    }
+
+    public static void checkArgument(boolean expression, Object errorMessage) {
+        throw new UnsupportedOperationException();
+    }
+
+    public static <T> T checkNotNull(T reference) {
+        throw new UnsupportedOperationException();
+    }
+
+    public static <T> T checkNotNull(T reference, Object errorMessage) {
+        throw new UnsupportedOperationException();
+    }
+
+    public static void checkState(boolean expression) {
+        throw new UnsupportedOperationException();
+    }
+
+    public static void checkState(boolean expression, String message) {
+        throw new UnsupportedOperationException();
+    }
+}